Self-defrosting refrigeration system



Patented Feb. 15, 1949 with SELF-DEFRO STING REFRIGERATION SYSTEM Peter J. Gaylor, Union, N. 3.

Application October 11, 1944, Serial No. 558,279

l Claims.

This invention deals with refrigeration and} more particularly, with the manufacture of selfdefrosting refrigerator coils employing brine as a refrigerant. It is well known in the refrigerator art that refrigerator coils, when cooled, gradually accumulate condensed moisture from the atmosphere. This condensed water gradually freezes on the surface of the cooling coils, resulting in a hard, tightly adherent crust of low cold-transfer characteristics, thereby greatly impairing the efflciency of the refrigerator and necessitating periodic warming up and thawing out of the coils.

Recently, improvements have been made in this direction by the application on the outer coil surface of an anti-freeze grease containing a freezing-point-lowering substance. Such an operation, although improving the situation somewhat.

- still is not a permanent solution and involves considerable trouble in periodic application ofthe messy composition.

The present invention involves a permanent solution to the problem and comprises the manufacture of refrigerating coils from a porous material, the porosity being of such a degree as to enable the cooled brine refrigerant to ooze out of the pores slowly but at a rate such that substantially no adherent ice encrustation takes place on the outer surface of the coils. In the case of calcium chloride-sodium chloride brine which is made to ooze out of the pores of the coil material, the ooze on the outer surface gradually absorbs and dissolves the condensed moisture from the atmosphere and drips from the coils, thereby allowing the formation ofa new film of fresh brine for continuous removal in this manner.

In some instances a loose scale formation may be produced which is readily removed by rubbing the ice formation with a hard object. The brine solution may be allowed to drip from the coils to receptacles on the floor, or it may be caught in pans suspended underneath the coils and piped outside of the refrigerator. The amount of brine 2 agents such as lactic acid salts, mold inhibitors like the propionates, and the like. Non-toxic substances are preferable.

iii)

ooze may be regulated by the porosity of the coil material, the pressure on the brine in the coils, the temperature, etc. A small amount of glycerine, glucose, or similar hygroscopic substance 'may be added to the brine to prevent crystalplugging of the pores by crystallization of salt during periods of non-use. Othersubstances which may be added to the brine are soluble oils, amines and other corrosion inhibitors, wetting agents and other surface-active substances, such as polar compounds of the alkyl succinic acid type which forma tenacious film on metal surfaces to the exclusion of water, rust-suspending and pressure.

The ,material from which the refrigerating coils are to be made is preferably one of high heat conductivity, as for example powdered metal which has been formed under pressure by "powder metallurgy" and sintered, if desired. Powdered iron and its alloys are suitable for this purpose, although it is possible to employ powdered aluminum, copper, bronze, brass, chrome-nickel alloys, or any other material of construction such as carbon, sintered glass, and the like. It is also possible to cast pipes from metal admixed with sand, carbon, etc. to give porosity thereto by treatment with reagents, burning, etc.

The invention may be more clearly understood from the drawing in which numeral i represents a-portion of a refrigerator having insulated walls 2. Suspended on the wall is header 3 from which, extend three coils 4 made of pressed and sintered stainless steel powder carrying chilled brine under this layer dissolves condensed water from the air,

it forms drops which are collected in trough 6 as layer I and gradually flows out of tube 8 to the outside of the refrigerator into a collecting tank. Tube 8 is preferably lagged with lagging 9 outside of the refrigerator so as to retain the cold in the brine.

Header 3 is fed with brine under pressure by pump ill which takes suction from line H coming from a storage tank. The pump forces the cold brine through line l2 and valve i3, thence into header 3. Lines H and I! are preferably lagged with lagging i4.

The other header iii, in which coils 4 are fitted, allows the warmed brine to pass into line i6. thence outside the refrigerator through line ll lagged with lagging i8, and throttle valve is which controls the amount of brine flowing through coils 4 as well as the pressure of the brine therein. The brine then leaves through line 20 and is run through a cooler for recirculation to the pump. The solution coming out of line 9 may be fortified with salt, cooled, and recycled with the material from line 20.

The term brine includes any refrigerating medium which is liquid at normal temperature It is desirable to employ cheap, non-toxic compounds which may be recycled, if desired. Water solubility is a desirable but not an essential characteristic. Sodium, calcium,

- magnesium and similar metal salt solutions are among the media normally employed in refrigerating systems.

The porosity necessary to effect the desired result depends upon the pressure of the refrigerating medium in the coils, its composition and viscosity, the rate of water condensation on the surface of the coils, etc. It is preferable to select the minimum porosity required and to adjust the amount of ooze (necessitated by changing conditions) by the pressure impressed upon the refrigerating medium. The higher the pressure, the greater will be the amount of ooze through the pores. and the more condensate-will be prevented from sticking to the outer refrigerating surfaces.

In order to insure the same rate of ooze in all coils in a system, it is possible to vary the porosity,

employing the lower porosity in the higher pres-' sure units. It is also possible to employ a coil of such low porosity as to allow very little, if any, ooze under normal operating conditions, thereby letting frost build. up loosely on the. outside coil surface. When defrosting is considered necessary, the pressure on the refrigerant liquid may be raised, thereby allowing sufficient flow through the coil wall to remove the frost deposit. This may be run periodically and controlled by a clock mechanism whereby cooling at normal brine pressure is employed for a predetermined interval after which the pressure on the brine is increased for an interval sufficient to insure a substantially clean coil surface, and thereafter the pressure is reduced back to normal.

I claim:

1. The method of refrigeration employing a normally liquid refrigerating medium, cooled to below the freezing point of water, under conditions tending to form a coating of frost on the outside of the refrigerating coils, comprising passing said cooled liquid medium through porous refrigerating coils under pressure sumcient to cause said medium to ooze out slowly through said pores and cover the outer surface in an amount sufllcient to prevent or remove the formation of adherentcrust-like deposit of frost.

2. The method of refrigeration according to claim 1 in which the refrigerating medium is a brine and said brine is passed through said coils continuously at a rate sufficient to continuously keep the outer surface of said coils free of frost deposit while they are in use, and continuously draining off the oozed material away from the coils.

3. The method according to claim 2 in which the amount of ooze is controlled by varying the pressure impressed upon the refrigerating me.-. dium.

' are made of compressed powdered metal.

6. A system according to claim 5 in which the medium contains a hygroscopic agent in amount sufficient to prevent crystallization of any salts which may form upon heating of the coils.

7. A system according to claim 5 in which the medium contains a surface-active agent.

PETER J.- GAYLOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,621,766 Bulmer Mar. 22, 1927 7 2,182,788

Cornell, Jr Dec. 12, 1939 

